Low Eutectic Temperature Research Articles

THE EFFECT OF ALLOYING ADDITIVES AND PROCESS PARAMETERS ON THE SOLIDIFICATION CHARACTERISTICS OF THE ALUMINIUM ALLOY AlSi7Mg0.3

We have investigated the aluminium alloy AlSi7Mg0.3, which is used in the production of castings. Melting was carried out in an electric resistance furnace. Casting was done into measuring cells with thermocouples for simple thermal analysis. Six samples that differed in terms of the additives used for grain refinement and inoculation, with two different holding times, were cast. An alloying material AlTi5B1 was used for grain refinement. The inoculation effect on the solidification was studied with the addition of the inoculant AlSr10. The temperature of the melt in the furnace was 750 °C and the melting time was one hour and ten minutes. Firstly, the samples were cast, the melt was cooled, solidification occurred and finally it was cooled down in the solid state. During the entire cooling process, the temperature as a function of time was measured and the cooling curves were obtained. After the casting, samples for metallographic inspection were prepared. The cooling curves show that in samples with a longer holding time, the additions of either the inoculant or the grain refinement agent, had a better effect. This is evident with a higher maximum liquidus temperature TLmax in sample Ti10 and lower maximum eutectic temperature TE1max in sample Sr10 in comparison to the basis alloy. The same we can conclude from the microstructure analysis of the samples. The samples with inoculant and with a longer holding time, possessed a finer eutectic structure (αAl+βSi), than the samples with the shorter holding time. The same applies for the samples with grain-refinement additions. The estimated grain sizes were smaller in the sample with the longer holding time.

A study on D2O/H2O-hydrohalite from Raman spectroscopy

The cryogenic phase behaviors and Raman spectra for D2O/H2O−NaCl solutions were observed and measured at temperatures down to 173.15 K. The (ice + hydrohalite) eutectic temperature of D2O−NaCl solutions is ∼255.95 K, 4 K higher than that of H2O−NaCl solutions. On the Raman spectral patterns, the four characteristic peaks of NaCl·2D2O hydrohalite are displayed to be more scattered than those of NaCl·2H2O. The third peak is easier to appear for NaCl·2D2O than for NaCl·2H2O that more cooling-heating runs and higher NaCl concentration are needed for this peak of NaCl·2H2O to be prominent, which indicates that NaCl·2D2O crystallizes more easily than NaCl·2H2O. We assign the 1st peak to the OD/OH stretch vibration of local water, and assign the 2nd, 3rd and 4th peaks to the OD/OH stretch vibrations of coordinating water respectively with D2O/H2O·Na+, Cl−···D2O/H2O·Na+, and (Cl−)2···D2O/H2O·Na+ interaction configurations. The harder crystallization of hydrohalite and lower eutectic temperature for NaCl·2H2O than for NaCl·2D2O are ascribed to the O–D···Cl− > O–H···Cl− and O–D···O > O–H···O hydrogen bonding interactions.

Molecular dynamics simulation of microstructure and thermophysical properties of LiCl–CaCl2eutectic molten salt

AbstractChloride molten salt systems are widely used as electrolytes for molten salt electrolysis because of their relatively low eutectic temperatures and good thermal stability, but there is a serious lack of data on the thermophysical properties of chloride molten salts at elevated temperatures, whereas the nature of the electrolyte is very important for the electrolysis process. In this paper, the variation of the microstructure and thermophysical properties of the binary mixed LiCl–CaCl2molten salt system with temperature and composition is calculated using molecular dynamics (MD) simulations based on the BMH potential. The microscopic conformations observed in LiCl–CaCl2molten salts are mainly irregular, distorted tetrahedra and octahedra, which dynamically coexist, as analyzed by the radial distribution function, coordination number and angular distribution function. In addition, the effects of temperature and composition on the density, ionic self-diffusion coefficient, shear viscosity, and ionic conductivity of the molten salts were investigated, and the relationships of the thermophysical properties of LiCl–CaCl2molten salts with temperature and composition were obtained, which provide fundamental thermophysical data for the molten salt electrolytes.

Water dynamics in eutectic solutions of sodium chloride and magnesium sulfate: implications for life in Europa's subsurface ocean and ice shell.

Liquid water is essential for life as we know it and the coupling between water and biomolecular dynamics is crucial for life processes. Jupiter's moon Europa is a good candidate for searching for extraterrestrial life in our outer solar system, mainly because a liquid water salty ocean in contact with a rocky seafloor underlies its ice shell. Little, however, is known about the chemical composition of the subglacial ocean of Europa or the brine pockets within its ice shell and their impacts on water dynamics. Here, we employ 1H, 17O, 23Na and 35Cl NMR spectroscopy, especially NMR spin relaxation and diffusion methods, and investigate the mobility of water molecules and ions in eutectic solutions of magnesium sulfate and sodium chloride, two salts ubiquitously present on the surface of Europa, over a range of temperatures and pressures pertinent to Europa's subglacial ocean. The NMR data demonstrate the more pronounced effect of magnesium sulfate compared with sodium chloride on the mobility of water molecules. Even at its much lower eutectic temperature, the sodium chloride solution retains a relatively large level of water mobility. Our results highlight the higher potential of a sodium chloride-rich than magnesium sulfate-rich Europa's ocean to accommodate life and support life origination within the eutectic melts of Europa's ice shell.

Effect of Y2O3 nanoparticles on enhancing microstructure and mechanical properties of oxide dispersion strengthened W alloy

Dispersion of oxide nanoparticles in W, leading to the dispersion strengthening of W alloys, has emerged as a viable strategy to overcome the brittleness of W. In particular, the introduction of stable Y2O3 as a secondary phase refines the grain and enhances the densification of W, leading to an increase in the density of sintered alloy. Thus, analyzing the composite effects of Y2O3 on the alloy, which has homogeneous dispersion of Y2O3 nanoparticles, can allow enhanced mechanical properties of the W-Y2O3 alloy. However, to date, most studies have focused on synthesis methodology for nanocomposites, which is advantageous to grain refinement and dispersion. It is worth paying attention to the interaction in the W-Y2O3 system, such as the ternary oxide system (W-Y-O) with a low eutectic temperature and the possibility of liquid-phase sintering, which has been reported a few. In this study, the effect of Y2O3 nanoparticles on the microstructure and micro-Vickers hardness of W was experimentally evaluated. W-Y2O3 alloys with precisely controlled compositions from 1 wt% to 10 wt%Y2O3 were successfully fabricated using an ultrasonic spray pyrolysis process and a subsequent spark plasma sintering. The proposed process yielded Y2O3 nanoparticles with uniform dimensions and distributions even after sintering. Furthermore, the formation of Y2WO6 and a liquid-phase sintered structure, as products of the interaction between W and Y2O3 depending on the Y2O3 fraction, were observed, and thermodynamical formation routes were suggested. Evidently, the W-2wt%Y2O3 sintered alloy, with uniformly dispersed Y2O3 nanoparticles (<50 nm), exhibited an improved hardness of 7.21 ± 0.15 GPa, as the W grains were refined to approximately 760 nm, and their density increased to 96.48%.

Unexpected spinodal decomposition in as-cast eutectic high entropy alloy Al30Co10Cr30Fe15Ni15

By integrating calculation of phase diagram (CALPHAD) simulations, ab initio molecular dynamics (AIMD) and experimental validation, we shed light on the unexpected spinodal decomposition in as-cast Al30Co10Cr30Fe15Ni15 alloy, as opposed to the eutectic BCC/B2 microstructure predicted by CALPHAD. We showed that the eutectic high entropy alloy (EHEA) and spinodal decomposition (SD) may be correlated with each other. A shift from as-cast EHEA to SD can be triggered by the strong short-range ordering in the EHEA liquid phase and high configuration entropy of the metastable phase. CALPHAD showed that the low eutectic temperature of Al30Co10Cr30Fe15Ni15 alloy is stabilized by the short-range and topological ordering (SRO), rendering a small undercooling ΔT for partitionless solidification of the metastable B2 phase. AIMD calculations showed that the particular metastable-like liquid preordering might reduce interface energy between the eutectic liquid and saturated B2, facilitating metastable saturated phase formation even with a small undercooling and suppressing the eutectic reaction. The single B2 phase might have solidified in the spinodal region of the phase diagram resulting in a shift from as-cast EHEA to SD. The interplay between SD and EHEAs presents an alternative route to explore spinodal HEAs by simple as-casted samples without lengthy heat treatments for homogenization.

Dissimilar ultrasonic spot welding of rare-earth containing ZEK100 magnesium-to-aluminum alloy with a zinc interlayer: Microstructural evolution and mechanical properties

The purpose of the present study was to identify microstructural changes at both Mg/Zn and Al/Zn interfaces of ultrasonic spot welded joints between a rare-earth containing ZEK100 magnesium alloy and an AA6022 aluminum alloy with a zinc interlayer, focusing on their effect on the tensile lap shear strength. During ultrasonic spot welding (USW), the diffusion or reaction was observed to occur at both interfaces, with the reaction being much faster at the Mg/Zn interface than at the Al/Zn interface. This was attributed to the higher diffusion rate of Zn in Mg and lower eutectic temperature in the Mg-Zn system along with the higher specific heat capacity and lower thermal conductivity of magnesium. With increasing welding energy, the diffusion layer at both interfaces increased. However, the diffusion layer at the Al/Zn interface was appreciably thinner than that at the Mg/Zn interface. While the eutectic (or eutectoid) structure containing Mg7Zn3, MgZn2 and MgZn intermetallic phases appeared at the Mg/Zn interface, the diffusion layer at the Al/Zn interface consisted of only Al and Zn based solid solution. The joining mechanisms were mainly mechanical interlocking and metallurgical bonding which were enhanced by grain refinement at both interfaces stemming from dynamic crystallization during USW. The peak tensile lap shear strength of the present Mg-Al dissimilar joints was attained at a welding energy of 1000 J, and the failure occurred in the diffusion layer at the Mg/Zn interface.

Preparation of Ammonium Persulfate/Glycerol based Novel Deep Eutectic Solvent under controlled conditions; Characterizations, Physical properties

A mixture of pure compounds is a deep eutectic solvent (DES) if it has a low eutectic point temperature and remains liquid at operating temperatures within a specific composition range. They are prepared by a combination of salt with hydrogen bond donor (HBD) moiety to some definite molar ratio. In the current study, a novel deep eutectic solvent was prepared by combining ammonium persulfate and glycerol in a 1:1.2 molar ratio using a discrete ramp input temperature response to prevent an uncontrolled reaction that could result in the emission of smoke and potential bursting. The affinity of ammonium persulfate for mixing with other HBDs was not significant. Moreover, the bonding behavior of the novel deep eutectic solvent was determined through FTIR spectroscopic analysis, which confirmed the physiochemical combination of its constituents and indicated the successful preparation of the DES, as evidenced by the significant shift of its characteristic peaks. The photoluminescence spectroscopic study was carried out to get insight about the electronic properties of the DES sample. The relationship between electrical conductivity rise with temperature was studied via a calibrated digital hand-held conductivity meter. The physical properties such as density, viscosity, surface tension, and freezing point of the immaculate DES at different temperatures were also reported. The variation in physical characteristics allowed the prepared DES to be appropriate for miscellaneous applications.

Preparation and application of low-temperature binary eutectic lauric acid-stearic acidSiO2 phase change microcapsules

Most phase change materials developed in current research have high phase change temperatures, making them challenging to use in buildings. To solve this problem, the microencapsulated phase change materials (MPCMs) with low eutectic temperature were prepared by interfacial polymerization using binary eutectic of lauric acid (LA) and stearic acid (SA) as the core material and silica as the shell material. And the phosphogypsum-based phase change microcapsules (PG-MPCM) were prepared. Morphology, structure and thermal properties of microcapsules have been investigated. The differential scanning calorimetry (DSC) results indicate that the melting and freezing temperatures of MPCMs prepared under optimal conditions are 27.9 °C and 28.3 °C, and the latent heats of melting and freezing are 170.3 J/g and 155.7 J/g. The thermogravimetry (TG) analysis results confirm that the microcapsules have good thermal stability. There is no significant change in the latent heat of the microcapsules phase change after 300 melting/freezing cycling. The heat storage performance shows that PG-MPCMs have good heat energy storage capacity and temperature regulation ability. In general, the LA-SA/SiO2 microcapsule is suitable as the energy storage material for buildings.

Effect of annealing temperature on magnetic properties of a sintered Nd-Fe-B magnet after grain boundary diffusion with Dy70Cu30 alloy

Grain boundary diffusion process (GBDP) has been developed as an effective approach to increase the coercivity of sintered Nd-Fe-B magnets by regulating the compositions and phase distributions near grain boundaries. This work aims to explore how to select the optimum annealing temperature after GBDP. In this work GBDP was performed on a sintered Nd-Fe-B magnet using Dy70Cu30 alloy. After GBDP the low eutectic temperature of the grain boundary phases decreases from the initial 492 to 451 °C. The magnetic property dependent on different annealing temperatures near the low eutectic temperature was studied. The magnetic properties, especially the squareness factor of demagnetization curve show a strong dependence on the annealing temperature. After GBDP the optimal magnetic properties can be obtained after annealing just above the low eutectic temperature of the grain boundary phases. The mechanism is discussed based on the microstructure analysis.

Magnetron Sputtering Deposition of Lead-Free (SAC) Thin-Film Alloys and Mechanical Characterization Using Nanoindentation

Electronic packaging industries are in an ongoing transition to lead free soldering due to the adverse effect on environment and human health [1]. Sn-Ag-Cu (SAC) have been recognized as promising alternatives due to its low eutectic temperature, higher wettability and strength, superior resistance to creep and thermal fatigue. Surface roughness has a significant influence on mechanical parameters determined nanoindentation tests. Although research has been conducted to analyze the mechanical properties of bulk SAC material, there have been limited prior studies on SAC thin films and their mechanical properties since fabricating a smooth SAC thin film is a fundamental challenge. SAC thin films with four different Sn–Ag–Cu ternary eutectic composition: 96.5Sn-3.0Ag-0.5Cu, 95.5Sn-3.8Ag–0.7Cu, 95.5Sn-3.9Ag–0.6Cu & Sn-4.0Ag–0.5Cu will be deposited using RF magnetron sputtering with different deposition rates and annealed at various temperature to fabricate a smooth continuous film. Figures 1 and 2 depict SAC05 deposited using RF magnetron sputtering at Figure 1: SEM image of SAC-05 surface at 10,000X. 20W, 2.4 mTorr pressure, and argon flow flow rate of 20.5 sccm. Surface morphology will be examined using Field emission Scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Crystallinity of the deposited film will be examined using X-ray diffraction (XRD). Mechanical properties will be studied using nanoindentation [2]. Properties of the thin film will be compared with the bulk material with similar eutectic composition.References M. Abtew G. Selvaduray. (2000). Lead-free Solders in Microelectronics. Materials Science & Engineering. a Review Journal., 27(5-6), 95.Long, X., Wang, S., Feng, Y., Yao, Y., & Keer, L. M. (2017). Annealing Effect on Residual Stress of Sn-3.0Ag-0.5Cu Solder Measured by Nanoindentation and Constitutive Experiments. Materials Science and Engineering: A, 696, 90-95. Figure 1

Low-temperature transient liquid phase bonding via electroplated Sn/In–Sn metallization

Sn/In–Sn bonding interfaces obtained by the transient liquid phase (TLP) reaction were investigated for applications in low-temperature assembly. Bonding was achieved at temperatures below 150 °C with a low bonding pressure. Although a few voids were formed at the interfaces after bonding, the In–Sn metallization enabled low-temperature bonding due to the low eutectic temperature. A bonding mechanism to achieve this novel In–Sn low-temperature assembly was also proposed.

Water uptake by chlorate salts under Mars-relevant conditions

Chlorine is ubiquitous on Mars, some of it in the form of oxy-chlorine salts. Chlorine-containing salts have been found at several landing sites, including that of Phoenix and Curiosity, in the form of perchlorates and chlorides. Several intermediate states also exist, of which chlorate is the most stable. While perchlorates have received much attention in the past few years, chlorate salts are much less studied. The ratio of perchlorate to chlorate on Mars is not well-defined but may be approximately 1:1. Chlorate salts have similar properties to perchlorates: high solubility, low eutectic temperatures, and likely low deliquescence relative humidities. Laboratory studies were performed to determine the ability of sodium and magnesium chlorate salts to take up water vapor at low temperatures (296 K to 237 K). These studies were performed using a Raman microscope equipped with an environmental chamber and a single particle optical levitator equipped with a Raman spectrometer. The deliquescence of sodium chlorate (NaClO3) was found to be temperature-dependent with the average relative humidity (RH) values ranging from 68% RH at 296 K to 80% RH at 237 K. Additionally, there was a slight deviation between experimental deliquescence values for this salt and those predicted by equilibrium thermodynamics. The observed efflorescence (recrystallization) of NaClO3 occurred at lower RH values ranging from 18% RH at 264 K to 24% RH at 249 K, demonstrating the hysteresis common to salt recrystallization. Several experiments were performed below the reported eutectic temperature of NaClO3 which resulted in supercooling of the brine and depositional ice nucleation. Based on the supercooling effects observed during our experiments, a revised metastable eutectic temperature of 237 K is suggested for NaClO3 compared to the previously reported value of 252 K. Two phases of magnesium chlorate (Mg(ClO3)2) were observed and exhibited different water uptake behavior. The most common form of Mg(ClO3)2 appeared to be a hydrated, amorphous phase, Mg(ClO3)2 • X H2O(a) that continuously took up water when the RH was increased. This water uptake behavior was even observed at very low humidity values, 5.0 (±1.9)% RH, with little temperature dependence. This detectable water persisted down to RH values close to 0%, averaging 0.5 (±0.6)% RH with no visible temperature dependence. The deliquescence relative humidity (DRH) of the hexahydrate, Mg(ClO3)2 • 6 H2O, was found to range from 50.9 (± 7.5)% at 227 K to 55.8 (± 6.6)% at 224 K and was consistent with thermodynamic calculations. Under conditions measured by the Remote Environmental Monitoring Station (REMS) instrument at Gale Crater and conditions modeled in the shallow subsurface, magnesium chlorate, if present, likely interacts with water vapor during some diurnal cycles.

Mineralogy, fluid inclusions, and sulfur isotope studies of Ghar Rouban Barite (Pb-Zn) deposit, Western Algeria

The Ghar Rouban barite (Pb-Zn) deposit is hosted by the Paleozoic basement and by the Liassic cover. There is no observable cross-cutting relationship between the deposits in the basement rocks and those in the Liassic cover. The main ore types are replacements, open space fillings, breccias, and veins. The thickness and length of the massive barite ore range from 10 cm to 3 m and 60 to 100 m, respectively. The ore minerals include galena, sphalerite, chalcopyrite, barite, quartz, and hematite. In this study, field observations, mineralogical, microthermometric, and sulfur isotope data are used to constrain the possible sources of the ores fluids and the possible age of mineralization. Fluid inclusions from barite reveal homogenization temperatures ranging between 100 and 150°C. Last melting of ice indicates salinities about 19 to 21 wt% equivalent-NaCl, but the low eutectic temperatures indicate that the fluid belongs to NaCl-CaCl2-H2O system. The δ34S values of barite minerals reveal a variation from 21.3 to 29.4‰. The lower values (21.3‰) are recorded in barites hosted by the Hercynian granite. The fluid inclusion compositions suggest that the ore-forming fluid was originally derived from seawater and was mixed with magmatic fluid.

Electrolysis of Lithium-Free Molten Carbonates

Electrochemically converting CO₂/carbonate to functional carbon materials and oxygen in molten carbonates has been viewed as a promising approach to tackling the environmental and energy challenges. Until now, most molten carbonate electrolyzers have focused on lithium-based molten salts due to their relatively low eutectic temperature and thermodynamic feasibility. However, the use of lithium-based molten salts will be constrained by its limited resource. Herein, the electrolysis of lithium-free molten carbonates (MCO₃–Na₂CO₃–K₂CO₃, M = Mg, Ca, Sr, and Ba) is systematically studied. Using the low-cost Ni-based inert anode, high value-added carbon and oxygen are prepared in the molten carbonates containing CaCO₃, SrCO₃, and BaCO₃. In addition, the solubilities of alkaline-earth metal oxides (MO) in molten carbonates are measured and the results show that MgO, CaO, and SrO are nearly insoluble and BaO is soluble (8.62 wt % BaO in 10 wt % BaCO₃–Na₂CO₃–K₂CO₃, 750 °C) in the corresponding alkaline-earth metal carbonates. Based on the solubility difference of oxides, two different electrolysis mechanisms are proposed—first, electrochemical reduction of CO₂ if MO is soluble in molten carbonate with the production of C and oxygen; second, electrolysis of carbonate with the production of MO, C, and oxygen.

Microstructural evolution and liquation cracking in the partially melted zone of deposited ERNiCrFe-13 filler metal subjected to TIG refusion

The microstructure of ERNiCrFe-13 multipass weld metal has been shown to contain Laves/γ or σ/γ eutectic constituents that can increase susceptibility to solidification and weld metal liquation cracking resulting from the low eutectic reaction temperature. Under poor heat dissipation conditions such as on the edge of large thickness welded components, a partially melted zone (PMZ) may form in the weld metal during multipass welding. The microstructural evolution and liquation cracking susceptibility of this PMZ in ERNiCrFe-13 multipass welds have received little attention. In the present study, a tungsten inert gas (TIG) refusion process is used to simulate a thermal cycle with a long elevated temperature dwell time in order to investigate the microstructural evolution and liquation cracking in the weld metal PMZ. The results show that the eutectic microstructures in the PMZ evolve into three eutectic morphologies after TIG refusion, including long linear chains extending perpendicular to the boundary between the refusion zone and PMZ, skeletal structures, and fine lamellar networks. This evolution contributes to constitutional liquation occurring at the γ/Laves and γ/σ interface. Nb and Mo play a leading role in the constitutional liquation of γ/Laves and γ/σ eutectic microstructures, respectively. Liquation cracking in the PMZ is shown to occur along the linear chain grain boundaries resulting from constitutional liquation.

Comparative Study of Silicon Nanowires Grown From Ga, In, Sn, and Bi for Energy Harvesting

A high density of silicon nanowires for solar cell applications was fabricated on a single crystalline silicon wafer, using low eutectic temperature metal catalysts, namely, gallium, indium, tin, and bismuth. The use of silicon nanowires is exploited for light trapping with an aim to enhance the efficiency of solar cells. Additionally, we have optimized the deposition parameters so that there is merely deposition of amorphous silicon along with the growth of silicon nanowires. Thus, it may improve the stability of silicon-based solar cells. The different catalysts used are extensively discussed with experimental results indicating stable growth and highly efficient silicon nanowires for photovoltaic applications. To test the stability, we measured the open-circuit voltage for four hours and the change in voltage was ±0.05 V. The fabrication of all-crystalline silicon solar cells was demonstrated using the conventional mature industrial manufacturing process that is presently used for the amorphous silicon solar cells. To summarize, this research compares various post-transition metals as a catalyst for the growth of nanowires discussing their properties, and such silicon nanowires can be utilized in several other applications not only limited to photovoltaic research.

The effects of metallic additives on the microstructure and mechanical properties of WC-Co cermets prepared by microwave sintering

The present work investigated the effects of Mo and Si metallic powders on the microstructure and mechanical properties of WC-5wt%Co cermets prepared through fast microwave heating process. Accordingly, 5 wt% Mo and 5 wt% Si were added separately to the WC-Co cermet and intensive mixing was performed using a high-energy ball mill. The prepared samples were sintered at 1400, 1500 and 1600 °C without any soaking time. The XRD patterns demonstrated WC peaks as the dominant crystalline phase along with tiny peaks that could be attributed to the formed carbides and intermetallics as the reaction product. As expected, the mechanical properties of the cermets were improved by increasing the sintering temperature due to the increased density; then porosity was decreased. WC-Co-Si cermet sintered at 1600 °C obtained higher hardness (15.8 ± 0.1 GPa), bending strength (876 ± 16 MPa) and fracture toughness (15.8 ± 0.1), as compared to the WC-Co-Mo cermet, due to the lower eutectic temperature of the Co–Si binary phase in comparison to that of Co–Mo. Moreover, the microstructural investigations confirmed the formation of carbides and intermetallics with an almost uniform distribution of the phases in the composites.

Influence of tool offset on microstructure and properties of Mg/Al dissimilar alloys by friction stir welding joints at low heat input

The composition of intermetallic compounds and mechanical properties during friction stir welding of 2024 aluminum and AZ31B magnesium alloys was investigated by using offset tool at low heat input. The macrostructure of the Mg/Al joints was investigated by optical microscope, and microstructure characteristics were analyzed by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. The fracture section was also observed. It is found that the mechanical strength of the joint slowly decreases as the value of tool offset increases first and then decreases at the Al-side. The result showed that the joints have the best mechanical properties when offset 0.5 mm and the amount of IMCs is low. And it is found that only IMCs Al12Mg17 is found in the joints. Since Al3Mg2 and Al12Mg17 have eutectic temperatures of 450 °C and 437 °C, respectively, the offset caused the temperature to decrease during the FSW process, allowing Al12Mg17, with a lower eutectic temperature, to form easily.

Large-Scale Sonochemical Synthesis of Bi-Sn Eutectic Alloy Nanoparticles.

Lead-free Bi-Sn alloy is an alternative solder material with a low eutectic melting temperature and environmental compatibility. Although extensive research has been conducted on this Bi-Sn eutectic alloy, a lack of facile synthetic methods with scalability hinders the implementation of finepatterned interconnectors for emerging electronic applications. In this study, we employed a facile sonochemical synthetic method to synthesize Bi-Sn alloy nanoparticles in large quantities. Highenergy ultrasonication treatment of Bi-Sn bimetallic particles resulted in nanoparticle formation with repeated formation, growth, and collapse of induced gas bubbles. The size of the nanoparticles was controlled from 92 to 506 nm of the mean diameter with variations in ultrasonication power and irradiation time. The nanoparticles exhibited a stable eutectic melting point at 139.8 °C. Interestingly, the sonochemically synthesized nanoparticles exhibited coexistence of metastable Bi2Sn and stable Bi-Sn phases. Finally, we demonstrated that Bi-Sn eutectic nanoparticles could be synthesized at a gram scale of approximately 1.7 g for future mass production.